Screw

The ScrewFastener fastener penetrates through all the given parts with a countersunk phillips head screw.

The last part’s hole is a pilot hole.

import cqparts
from cqparts.constraint import Fixed, Coincident
from cqparts_fasteners.fasteners.screw import ScrewFastener
from cqparts_misc.basic.primatives import Box

class Thing(cqparts.Assembly):
    def make_components(self):
        base = Box(length=20, width=30, height=15)
        top = Box(length=40, width=20, height=5)
        return {
            'base': base,
            'top': top,
            'fastener': ScrewFastener(parts=[base, top]),
        }

    def make_constraints(self):
        base = self.components['base']
        top = self.components['top']
        fastener = self.components['fastener']
        return [
            Fixed(base.mate_bottom),
            Coincident(top.mate_bottom, base.mate_top),
            Coincident(fastener.mate_origin, top.mate_top),
        ]

Resulting in:

thing = Thing()
display(thing)

FreeCAD’s render may be more clear (literally).